The electronic contents market is explosively growing complementary to the terminal market [International Digital Publishing Forum, Yankee group, 2010]. Among contents, books in an electronic form, namely e-book contents, are most abundant and vast and are recognized as the most important contents. The terminal-to-contents platform compositions such as iPad to iBookStore, Kindle to Amazon, and Biscuit to Interpark are good illustrations. However, such e-book contents may be sold only when a terminal allowing the e-book to be read is provided. Therefore, the e-book terminal market is an essential factor of the e-book contents market. Evaluation factors of the e-book terminal include visibility, portability, price, navigation function, annotation function or the like. Among them, the navigation function is a most basic element of a user interface of the e-book and should be natural and efficient in order to meet the satisfaction of users. Even though terminals such as iBooks, Kindle, and eDGe receive attention in the existing market due to distinctive user interfaces, they cannot yet provide a natural support as if a user reads a paper book. As a major problem, users feel inconvenience during navigating in an e-book, namely when a user who is reading a section of the e-book navigates in the e-book to read another section.
First, in US Patent Publication US2010/017518, an e-book utilizing a virtual page turn is implemented by using a display such as an e-book terminal and a computer monitor. However, in a mobile environment, a computer monitor is not available, and the e-book terminal also lays a burden due to its volume and weight.
Second, in an implementation of an e-book disclosed in US Patent Publication US2009/0237367, when moving to a bookmark, a user should 1) call a bookmark menu, 2) choose a page in a bookmarked page list, and 3) click/push the chosen bookmark by means of touch or button manipulation. The three-stage menu selecting process increases cognitive burdens of the user and disturbs reading.
Third, in a conventional e-book, in order to enlarge or reduce a size, a user should touch a screen and make a pinching gesture perform keyboard or mouse manipulations, which are not natural.
Fourth, in an existing e-book, in order to move to a distant position, a user should use a scroll bar (iBooks of iPad) or utilize a graphical user interface (GUI) such as a thumbnail which fills the screen. However, while manipulating graphic objects displayed when the GUI menu is called, a user may forget the contents of the e-book the user was reading.
Fifth, an existing e-book gives only a ‘visible feedback’ like turning over pages. Therefore, 1) a user cannot feel as if he uses a real book, and 2) a user who is turning over pages fast cannot stop at an accurate position.